Conveying devices of this kind are used in logistics processes for fully automated and semi-automated conveying of articles, and convey, for example, parcels, pallets, merchandise and other goods from an entry point to a exit point. In complex conveyor systems, the entry points and the exit points are sometimes far apart. They are connected to each other by conveyor segments. A conveyor segment may form a section of a conveyor line, which includes a conveyor drive that can be controlled by the control unit and, if necessary, a sensor for detecting a product being transported in the conveyor segment. A conveyor segment can also be formed by branching, by merging, by an elevator or a lowerator, by a sorter or a singulator, and these devices' own actuators and sensors can be controlled and monitored by the respective control unit of the conveyor segment. The conveyor segments form the architecture of a conveyor system. They allow complex conveying devices to be implemented.
The control units monitor and control one or more of these conveyor segments. The conveying process within the conveyor segments is monitored and influenced with the aid of suitable sensors and actuators. Depending on requirements, suitable sensors must detect the spatial position, size, and identification, including the parameters of control elements and the articles being conveyed. Typical sensors used in this connection include photoelectric barriers, photoelectric sensors, optical scanners, and proximity switches. The articles are moved, braked, and changed in their orientation or direction by means of the actuators. Examples of typical actuators include pneumatic or hydraulic cylinders, stepper motors, roller drives, belt drives, and vibration drives, inter alia.
A conveyor segment may usually include a zone sensor, a plurality of conveyor rollers and at least one conveyor drive. A zone sensor is a photoelectric barrier, a photoelectric sensor, an optical scanner or a proximity switch, for example. A conveyor drive is a motorised roller, a drum motor, or a geared motor with a coupling element, for example. Conveyor rollers, motorised rollers and drum motors are usually mounted in a frame and move the article being transported by contact with the driven rollers.
A control unit controls the conveying process, for example, the activity status of the conveyor drive and its direction of rotation. Control units of conveyor segments generally have an interface as well, via which it is possible for control commands to be received from a central control unit or from neighbouring control units of neighbouring conveyor segments. These interfaces are mostly digital and are based on standardised communication buses such as EtherCAT, Ethernet/IP, Profibus and ASi, thus allowing bus communication between or to the individual control units of the conveyor segments. By using conveying devices interconnected by a bus, it is possible for controlling activities to be decentralised. The advantageous aspect of this is that basic functions can be stored in a control unit, thus simplifying the installation, setting up, and servicing of conveying devices.
Control units for conveying devices are basically known from the prior art. Aspects of a control unit in a conveyor line controller are described in U.S. Pat. No. 8,757,363 B2. Different operating modes for conveying articles are described, as are methods for setting up conveyor devices. EP 1 454 851 B1 describes a method that is implemented in a control unit and which, jointly with other control units, controls roller conveyors of several conveying zones in a described procedure for influencing the flow of articles.
It is necessary in conveying devices to minimise the downtimes of the conveyor device and the commercial losses this downtime involves. Downtimes result, for example, from malfunctions in the flow of products or from malfunctions or wear and tear of the mechanical parts of the conveying device. Malfunctions may also result from defects in electronic components, such as the control unit. Whereas disruptions in the flow of articles, such as jamming of articles, can mostly be remedied quickly by a user manually intervening, eliminating malfunctions of the mechanical components of a conveying device is more time-consuming in most cases. It is possible to guard against such component failure by defining service intervals and performing routine checks. Defining service intervals is uncommon in the case of electronic components, because component failure cannot normally be foreseen or identified from visible signs of wear and tear. For that reason, failure of electronic components is predominantly acute. Sensitive electronic components can also be damaged or destroyed by departure from the electric input parameters or by mechanical impacts, for example by collisions with vehicles or workpieces.
Defects in electronic components are mostly irreparable and require complete replacement of the components or of complete modules. For example, it is impracticable, in the environment of a conveying device, to replace single electronic components or electronic modules of a control unit, in the form of printed circuit boards. Instead, a defective control unit of a conveying device is replaced by a control unit that works. Some present-day control units are technically designed in such a way, to simplify replacing a control unit, that only a few electrical connections need to be made. Nevertheless, replacing a control unit usually requires skilled personnel to configure and integrate the replacement control unit within the system. This can result in significant downtimes of the conveying device and associated commercial losses.